Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
  • B01J27/14—Phosphorus; Compounds thereof
  • B01J27/186—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J27/188—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium with chromium, molybdenum, tungsten or polonium
  • B01J27/19—Molybdenum
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
  • C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
  • C07C51/25—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of unsaturated compounds containing no six-membered aromatic ring
  • C07C51/252—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of unsaturated compounds containing no six-membered aromatic ring of propene, butenes, acrolein or methacrolein

Definitions

• GB-A-1 473 035 proposes catalysts which, in addition to Mo, Cu and P, contain at least one alkali metal, selected from the group Li, Na, K, Rb, Cs, and at least one metal, selected from the group Sb, V, W, Fe, Mn, Sn included.
• Oxidation catalysts which are produced in the presence of high chlorine ion concentrations of about to 5 equivalents per equivalent of molybdenum, such as, for example, the Mo, P, W-containing catalysts of US Pat. Nos. 4,212,767 and 4,272,408 or the Mo, P, Sb and optionally W-containing catalysts according to US-A-39 65 163 show a relatively good catalytic activity with short operating times, but it is difficult to reproducibly produce long-lasting and sufficiently selective catalysts of this type.
• the catalysts mentioned tend to increase the formation of acetic acid if they are used in technically reasonable particle sizes of at least 3 mm.
• the catalyst components can optionally be used as oxides or acid anhydrides, but water-soluble compounds are generally preferred.
• Suitable molybdenum and tungsten compounds are, for example, ammonium molybdate, phosphomolybdic acids and their salts, ammonium tungstate, phosphotungstic acid and their ammonium salt.
• the compounds mentioned are preferred, in particular ammonium molybdate or phosphomolybdic acid as molybdenum acid and phosphotungstic acid as tungsten compound.
• phosphoric acid and its ammonium salts can advantageously be used as the source of phosphorus.
• Antimony and the cationic elements can be used in the form of their chlorides, but the total amount of chlorine ions in the preparation of the catalysts should be less than 0.3 mol, in particular less than 0.25 mol, per mole of molybdenum and free hydrochloric acid should not be used.
• the cationic elements Cu, Mn, Sn, Fe, Nb and Cr can be in various forms, e.g. B. as oxides, hydroxides or carbonates, such as Nb 2 0 3 , Sn (II) O, Cu (OH) 2 xCuCO 3 , or as formates, oxalates or acetates. Such salts are preferred over nitrates.
• Arsenic is advantageously added as ammonium arsenate or arsenic acid, although other compounds are also possible.
• the catalysts of the invention can generally be prepared in such a way that the combined solutions of the molybdenum, phosphorus and optionally arsenic compound first with the antimony compound, which is advantageously dissolved or finely dispersed in the aqueous solution of carboxylic acids, and then with the aqueous solution of the tungsten compound are combined.
• the additional components which may be used are generally added after the main component has been combined.
• the amount of the carboxylic acid is generally 0.02 to 2 mol, preferably 0.05 to 1.5 moles per mole of molybdenum.
• the carboxylic acids can advantageously be added as such, the formic acid, acetic acid, tartaric acid and citric acid, but especially the formic acid alone or in combination with the other carboxylic acids, being preferred.
• the carboxylic acid ions promote the formation of a particularly stable form of the phosphorus-containing heteropolyacid and its salts which, after drying, shaping and calcining, gives a catalytically particularly effective structure of the active catalyst.
• the drying of the aqueous solution or suspension of the components is generally carried out by evaporation in stirred tanks at temperatures below 140 ° C. or by spray drying at outlet temperatures between 80 and 140 ° C.
• the masses obtained are usually ground to particle sizes of 200 to 1200 ⁇ m and, if appropriate after the addition of customary carriers, such as SiO 2 or aluminum oxides, and, if appropriate, of lubricants, such as graphite, pressed to give spheres, tablets, rings or other shapes. You can then subsequently calcine or activate in the air, under nitrogen or a slightly reducing atmosphere at low gas flows and temperatures of 180 to 400 ° C., preferably from 22C to 380 ° C., in particular from 320 to 360 ° C.
• the carriers can also be added during the evaporation of the catalyst suspension, whereby the catalyst. gate components are deposited on the carriers.
• the dried unc-ground catalyst masses can be calcined without the addition of supports at the temperatures mentioned and then processed into shaped structures or on supports, in particular on spherical supports in the form of trays in a conventional manner, for. B. by the methods known from US-A-4 305 843 and 4 29i 247.
• the catalytically active compositions have only the structure of a disturbed heteropolyacid or its salts. x-ray diffraction lines. They are particularly suitable for the oxidation of methacrolein ZL methacrylic acid under conditions which are conventional per se in the gas phase, in particular when methacrolein is used as the starting material, which is produced by condensation of formaldehyde with propanal.
• oxygen and water vapor-containing gas mixtures are used as oxidizing agents, which are passed over catalysts which are generally fixedly arranged in catalyst beds bar, advantageously from 1 to 2.5 bar.
• the residence time of the gas mixtures containing methacrolein based on standard conditions is 0.5 to 5 seconds and residence times of 1 to 3 seconds at temperatures in the range from 200 to 340 ° C., in particular at 220 to 320 ° C.
• the reaction gases generally contain indifferent gases, especially nitrogen, and the oxygen is generally supplied as air.
• E can also be used as pure oxygen.
• the reaction gas generally contains carbon oxides, in particular if, after the methacrylic acid formed has been removed, residual reaction waste gas is returned as a diluent together with unreacted methacrolein to the oxidation reaction.
• the molar ratio of methacrolein: oxygen: water: inert gas in the reaction gas mostly 1: 1 to 6: 1 to 20: 4 to 50, preferably 1: 1.5 to 4: 2, to 10: 6 to 30.
• the methacrylic acid can be separated off from the hot reaction offgases in a conventional manner, usually by Quenching can be done with water.
• the methacrolein can be obtained by various methods, e.g. B. by gas phase oxida tion of tert. Butyl alcohol, isobutylene or C 4 mixtures or by condensation of propionaldehyde with formaldehyde.
• the use of the catalysts according to the invention is particularly advantageous if methacrolein is used, which is prepared by condensation of propionaldehyde with formaldehyde in the presence of salts of secondary amines or with aminals in the presence of acids in aqueous solution.
• the catalyst activity can be changed such that it increases continuously or in stages in the reaction tube in the direction of flow of the reaction gases. This can e.g. B. by diluting the catalyst m less active or inactive catalyst or support moldings or by using 2 or more catalysts with different activity and / or selectivity. It is also possible. However, the oxidation of methacrolein to methacrylic acid according to the invention in the fluidized bed fixed catalyst layers to be carried out are preferred.
• aqueous solutions of methacrylic acid are obtained which, if appropriate, additionally contain small amounts of acetic acid, maleic acid and acrylic acid. From the solutions of methacrylic acid obtained, this can be extracted in a conventional manner with suitable solvents, such as, for example, methyl methacrylate, and either esterified directly with alkanols or distilled from the extract by distillation and separated from the by-products.
• suitable solvents such as, for example, methyl methacrylate
• the unreacted methacrolein can be distilled from the aqueous condensate or z. B. driven out with steam and fed back to the oxidation reaction.
• the catalysts of the invention also show other oxidation reactions, for. B. in the oxidation of acrolein to acrylic acid or in the oxidation of substituted toluene derivatives to substituted benzaldehydes and benzoic acids good effectiveness and selectivity.
• methacrolein with a purity of 97 to 99% is used to test the catalysts, which contains small amounts of secondary amines and by-products of methacrolein synthesis from propionaldehyde and formaldehyde in addition to water and propionaldehyde.
• the parts and percentages therein relate to the weight.
• the parts by volume given in relation to the parts by weight relate to the liter to the kilogram.
• the dried mass is ground to a particle diameter of 0.4 to 1.2 mm and compressed to 3 x 3 mm tablets after the addition of 2% graphite powder.
• the tablets are heated in air to 355 ° C for 6 hours.
• the catalyst has the formal composition
• Example 2 As in Example 1, a catalyst was prepared except that the antimony trichloride used antimony (III) oxide in an amount of 14.6 parts. Under the test conditions of Example 1, but at a bath temperature of 284 ° C., the conversion was 84.8 mol%, the selectivity 83.7 mol%, the methacrylic acid yield 71 mol% and the yield of acetic acid 0 , 86 mol%.
• Example 2 further catalysts were produced and tested, with the change that tartaric acid, citric acid and oxalic acid were used instead of the formic acid.
• the amounts added and the test results are summarized in Table 2.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Materials Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
• Catalysts (AREA)

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• 1982
  • 1982-03-10 DE DE19823208571 patent/DE3208571A1/de not_active Withdrawn
• 1983
  • 1983-02-28 DE DE8383101939T patent/DE3364829D1/de not_active Expired
  • 1983-02-28 EP EP83101939A patent/EP0088328B1/de not_active Expired
  • 1983-03-01 US US06/470,942 patent/US4489170A/en not_active Expired - Fee Related
  • 1983-03-08 CA CA000423141A patent/CA1190539A/en not_active Expired
  • 1983-03-10 JP JP58038385A patent/JPS58189038A/ja active Granted

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